Method of and apparatus for honing



April 6, 1943. A. M. JOHNSON METHOD OF AND APPARATUS FOR HONING Filed May 8, 1939 2 Sheets-Sheet l April 6, 1943 A. M. JOHNSON METHOD OF AND APPARATUS lRl HO-NING Filed May 8, 2 Sheejbs-Seeb 2 Patented Apr. 6, 1943 2,315,794 METHOD F APPARATUS FOR HONING Albert M. Johnson, Rockford, Ill., asslgnor to Barnes Drill Co., Rockford, Ill., a corporation of Illinois Application May 8, 1939, Serial No. 272,334

19 Claims.

The invention relates generally to the art of dressing the internal surfaces of hollow bored work pieces of circular cross section, and more particularly to an improved method of and apparatus for honing relatively long work pieces having a gradually tapering bore.

Thel honing process which consists in relatively rotating and simultaneously relatively reciprocating a cylindrical abrasive tool and the Work has been found to be the most eicient and satisfactory method of dressing internal surfaces where a true contour and extremely smooth surface iinish is required. The use of this process has been limited, however, to dressing cylindrical work due to the necessity of maintaining the reciprocatory path of the tool substantially parallel to the surface operated on. This consideration has made it impractical to hone tapered bores, and it has accordingly been the usual practice to finish such bores by a grinding operation which, of course, is inherently incapable of producing the true contour and smooth nish obtained on cylindrical work by the honing process.

One object of the present invention is to provide an improved method of honing particularly adapted for dressing long tapered bores and capable of finishing such bores with a high degree of accuracy for roundness and straightness and with a mirror-smooth surface-finish.

Another object is to provide a novel machine for honing tapered bores in accordance with the improved method of honing.

Other objects and advantages of the invention will become apparent from the following detailed description of the construction and mode of operation of the exemplary honing machine illustrated in the accompanying drawings, in

which: Y-

Figure 1 is a side elevational view of a honing machine embodying the features of the inventhe tool is rotated and reciprocated relative to a statlonarily supported work piece. It is to be understood, however, that` the invention is in no wise limited to such machines but is readily applicable to other types of honing'machines.

`In carrying out the improved method of honing contemplated by the present invention with a machine such as that illustrated, the honing tool is rotated and simultaneously reciprocated through a stroke of sufficient amplitude to traverse the tool from one end of the work piece to the other. In the movement of the tool from the large end to the small end of the bore the abrasive elements are shifted radially outwardly or "expanded" with a relatively light pressure. Preferably suilcient pressure is supplied to hold the elements in operative engagement with the surface ofthe work and yet permit them to be cammed back progressively without injury to the elements as the diameter of the bore decreases. Alternatively, the tool expanding means may be arranged to gradually reduce the pressure applied as the tool moves into the small end of the bore.

Upon reverse movement of the tool and while it is traversing toward the large end of the bore, the abrasive elements are expanded with relatively high pressure to insure their continuous operative engagement with the walls of the bore. Preferably, the higher pressure is applied as the return movement starts although, if desired, the increase in pressure may be introduced gradually as the tool moves toward the large end of the bore. In this way, the tool is enabled to dress the bore to the desired true contour and extremely smooth finish with the same high degree of accuracy heretofore obtained in honing cylindrical bores. Moreover, the pressure exerted by the abrasive elements on the surface of the bore is adjusted so that the honing operation is performed emclently and without danger of injury to the tool.

vThe machine selected to illustrate the invention comprises generally an elongated frame or base which, as shown in Fig. 1, consists of a main section 5 and an outboard section or Work support 6 bolted or otherwise rigidly secured together in end-to-end relation. The main section of the base is provided with a longitudinally extending guideway for supporting and guiding a reciprocatory carriage or tool head l. In the particular machine illustrated, the guideway is formed by rigid guide bars 8 mounted on the side walls of the base section 5 in spaced parallel relation and the head 'l is supported thereon by means of spool-shaped rollers 9 which permit the head to move freely along the guideway but effectively prevent lateral movements of the same.

Journaled on the head 1 and projecting forwardly therefrom is a tubular spindle I which carries on its free end a honing tool II of suitable and well known construction. Such honing tools ordinarily comprise a series of elongated abrasive elements or honing stones I2 supported in a generally cylindrical holder I3 and movable radially therein to engage the surface of the work piece. In the case of tools designed for honing tapered bores, it is preferred to have the abrasive elements formed or set so that their outer or active surfaces are inclined with respect to the axis oi' the holder, the angle of inclination being substantially the same as the taper of the bore to be honed. The active surfaces of the elements are thus disposed substantially parallel to the walls of the bore.

The abrasive elements of the tool II are normally held in a retracted position by suitable springs and are moved outwardly to engage the work by means of a cam block I4 (Fig. 4) actuated by a rod I5 extending back through the spindle I0 to the tool head. Preferably, power actuated mechanism carried within the tool head vand reciprocable therewith is provided for shifting the actuating rod I5 to expand and contract the tool. 'I'his mechanism may be of the same general character as that disclosed in applicants copending application Serial No. 235,125, led October 15, 1938, which matured and as Patent No. 2,171,271, August 29, 1939, and is herein shown as comprising a piston I 3 secured to the inner end of the rod and operating in a hydraulic cylinder I1 carried on the head. The arrangement is such that the tool actuating mechanism is shifted forwardly to expand the tool upon introduction of pressure uid into the closed end of the cylinder I1. A coiled compression spring I8 acts to return the piston and the rod to normal position when pressure is removed from the piston, thus permitting the tool to contract in the usual Way through the action of its contracting springs.

In operating on a'work piece W supported on the base section 6, the tool is rotated and simultaneously reciprocated through a stroke of sufficient amplitude to trasverse the tool from one end of the work piece to the other. Preferably, the work piece is mounted with the larger end of its bore 20 facing the tool head. The tool is initially inserted therein while in contracted condition by an advancing movement of the head. The tool may then be expanded bythe power actuated mechanism provided for this purpose, and while so expanded is traversed over the work piece by reciprocatlon of the head.

In the exemplary machine, reciprocation of the head is effected by means of a pair of traction members, herein shown as flexible cables 2I, 22 (Figs. 1 and 4), each anchored at one end to the head and at the other end to a grooved cable drum 23 rotatably supported at one end of the base section 5. One of the cables, in this instance the cable 2I, leads directly to the drum while the other cable 22 is carried over a sheave 24 yieldably supported at the opposite end of the base section 5. With this arrangement, rotation of the cable drum 23 rst in one direction and thenl in the other direction winds up and pays out the cables alternately, thus drawing the head back and forth on the guideway to traverse the tool over the work.

While any suitable means may be employed for rotating the cable drum 23, the machine illustrated is equipped with a reversible rotary pressure fluid motor M (Fig. 4) for this purpose. The drive shaft of this motor carries a worm 25 cooperating with a worm wheel 26 rigid with the drum. Pressure fluid for operating the motor is supplied by a pump P arranged to be driven by an electric motor M--I which receives current from a power line comprising conductors L-I, L-2 and L-3. The pressure fluid is delivered to the motor through a hydraulic circuit in which is interposed the usual control valves including an on and 0H valve V for starting and stopping the motor and a reversing valve V-I for controlling its direction of rotation.

Control mechanism of well known character is provided for operating the reversing valve V-I to maintain the reciprocatlon of the head within the desired limits. This mechanism as herein shown includes a pilot valve V-Z of the usual type -arranged to control the supply of pressure fluid to the reversing valve operating cylinders. The pilot valve is operated by a pair of solenoids S and S-I energized alternately under control of limit switches LS and LS-I arranged to be closed by a switch operating member 21 carried by the head which coacts with the respective switches as the head approache the respective opposite ends of its working stroke. A third limit switch IIS-2 adapted to be engaged by the member 21 as the head approaches its fully retracted position operates to stop the machine in well known manner.

For rotating the tool II during its reciprocation, a motor M-2 mounted on the head is drivingly connected with the tool spindle by suitable gearing 28 enclosed in a housing 29 forming a part of the tool head. Current may be supplied to the motor M-Z from the power line conductors LI, L-2 and L3 either through a flexible cable or through bus bars and sliding contact brushes indicated diagrammatically at 30 (Fig. 4).

In order to enable the tool to perform its operation upon the work piece when it is rotated and reciprocated in the above manner, the abrasive elements I2 must be expanded into engagement with the surface to be dressed. Such expansion is effected by the mechanism, hereinbefore described, upon introduction of pressure fluid in the closed end of the tool expanding cylinder I1. Pressure fluid for this purpose is supplied by a pump P-I (Fig. 4) driven in this instance by the spindle rotating motor M-2. The pump is arranged to draw fluid from a sump or reservoir R formed in the head and to deliver the fluid under pressure to a pressure line 3|. Check valves CV arranged in the suction and the discharge lines of the pump in well known manner enable it to function properly when rotated in either direction.

To enable the attendant to control the expansion and contraction of the tool at will, a cut-off valve V3 is interposed between the pump P-I and the cylinder I1. shown, is normally biased to a position to connect the pressure line 3l to a return duct or drain 32 which returns the spent pressure fluid to the sump R, preferably discharging it over the various rotating parts and bearings within the housing 29 to lubricate the same. At the same time a feed line 33 leading to the closed end of the cylinder I1 is connected with a drain 32 which directs the spent pressure fluid back to the sump R. The spring I8 is therefore enabled to shift This valve, as herein for operating the valve V-3. This soleroid is energized by closure of a switch SW which connects the solenoid across power line conductors L--l and L-2.

When the work piece to be operated on has a tapered bore and is to be honed in accordance with the improved method hereinbefore described, the pressure exerted by the abrasive elements on the tool should be varied in alternate forward and return strokes of the head. This variation may be effected conveniently by varying the pressure of the fluid supplied to the tool expanding cylinder Il. To this end, the pressure line 3l is formed with a branch 34 adapted to be connected selectively with either of two' pressure control valves V--4 and V-5 through the medium of a two-position valve V-6.

The pressure control valves may be of any' sure while the valve V--5 is adjusted to open at afsubstantially higher pressure. Thus by connecting these valves to the branch line 34 at the proper point in the machine cycle the pressure of the fluid supplied to the tool expanding cylinders I1 may be regulated in the manner required for carrying out the improved honing method.

While the selective connection of the pressure controlled valve to the control line may be effected manually if desired, it is preferred to employ automatically operated control means for this purpose to insure proper timing of the connection with respect to the movement of the tool relative to the work. To this end, the valve V-B is biased to a position in which it connects the low pressure valve V-4 to the pressure line, as shown fin Fig. 4, and a solenoid S-3 is provided for operating the valve to its alternate position to disconnect the valve V-4 and connect the high pressure valve V-5 to the line..

Energization and deenergization of the solenoid S-3 are controlled by a switch SW--I adapted to interrupt the circuit for the solenoid during the forward movement of the tool head and to close the circuit while the head executes its return movement. Thus, the tool is expanded with low pressure when the switch is open and with high pressure `when the switch is closed. Failure of the switch to close at the proper time can therefore cause no damage to the machine as it simply results in keeping the tool pressure at the lower level.

A preferred form of the switch SW-s-l is illustrated in Fig. 3. As herein shown, the switch comprises a lever 35 pivoted intermediate its ends on a pivot pin 36 journaled in a split bracket 31 projecting laterally from the head. The inner end 38 of the lever extends into a suitable switch box or casing 38a mounted on the head and constitutes a switch operating member. To this end, the lever is arranged to shift a mov- Inthe"4 able contact point 39 into engagement with a. stationary contact point 40 when the lever is rocked in a counterclockwise direction.

The other end of the lever 35 extends outwardly toward the side wall of the base 5 and is equipped with a shoe 4l fitted with a. friction member 42 adapted to rub against a. vertical friction surface 42a on the wall. In order to enable the parts to accommodate themselves to the changes in position required to open and close the switch contacts, the shoe 4l is pivotally and yieldably secured to the lever 35. For` this purpose the outer end of the lever is arranged to project into a slot 43 in the back of the shoe v and is held therein by a pin 44 projecting through an elongated generally oval slot 45 in the lever. A coiled compression spring 46 bearing at one end against a flat surface 41 formed on one side of the pin and at the other end against the lever tends to hold the shoe in its forward position with the pin in the outermost end of the slot. The arrangement is such that the friction member 42 through its engagement with the surface 42*il during the forward movement of the head acts to hold the switch operating member against a stop 48 and to maintain the switch contacts 39 and 40 separated, that is, in open circuit position.

When the head starts its return movement, the frictional engagement of the element 42 with the wall 42a rocks the lever 35 in a clockwise direction and thus closes the contact 39 against the contact 40. As the effective length of the lever arm decreases, due to this rocking action, the spring 46 yields to prevent damage to the parts.

Due to the operation of the switch SW--I, as above explained, the circuit of the solenoid S3 is opened and the low pressure valve V-4 is connected to the pressure line so that the tool is expanded with relatively light pressure as it moves forwardly from the large end to the small end of the bore. Upon return movement of the tool, the switch is closed and the solenoid energized so that the high pressure valve is connected up and the tool expanded With relatively high pressure as it moves toward the larger end of the bore. Pressure/control is effected automatically, thus insuring proper performance of the honing operation and effectually guarding against damage to the tool.

In the event that the machine is to be used for honing ordinary work pieces in the manner heretofore employed, the pressure control mechanismv may be temporarily disabled by means of a manually operable switch SVV-2. As shown in Fig. 4, this switch is connected in series with 'the friction operated switch SW-I and the solenoid S-3, and when opened prevents the solenoid from energizing when the switch SW-I is closed. I

The operation of the exemplary machine in performing a honing operation in accordance with the improved method is briefly as follows:

The work piece W is clamped or otherwise.

rigidly secured to the base section 6 with the large end of the bore 20 facing the tool head. Ordinarily, this bore will be roughly machined to the desired tapered form before the honing operation is performed. When the work is properly set up, the pressure lvalves V--4 and V-5 are adjusted to operate at switches LS and LS-l are adjusted, of course, to determine the limit positions of the head in its working stroke. The valve V is then operated to direct the supply of pressure iluid through the reversing valve V-i to the motor M which rotates the 4drum 23 and advances the tool head toward the work piece. The limit switch LS-l is preferably of the well known skip stop type arranged to allow the tool head to pass in its forward movement without effecting the operation of the motor but acting on return movement of the head to reverse the same. Limit switch IS performs this function at the opposite end of the stroke. The head is accordingly reciprocated between the limits deiined by the two switches.

As soon as the tool is entered in the bore of the work piece, it is expanded by operation of the valve V-3 incident to the closure of the switch SW. While the tool is moving forwardly into the small end of the bore, the switch SW-I is opened and solenoid S-3 is deenergized, thus connecting the low pressure valve V4 to the pressure line. The tool is accordingly expanded with relatively low pressure so that the abrasive elements may be cammed back as the portion of the bore in engagement with the abrasive elements decreases progressively in diameter.

When the direction of movement of the head is reversed by the operation of the limit switch LS, the friction switch SW-I closes to energize the solenoid S-3 and thus connect up the high pressure valve V-5 in place of the low pressure valve. 'I'he tool is thus expanded with relatively high pressure during its return movement toward the large end of the bore and the abrasive stones are accordingly maintained in working contact with the walls oi the bore as it increases in diameter. In this way,the tool is enabled to operate efficiently throughout the entire length of the work piece and yet is eiectively protected from excessive `pressures which might damage the abrasive elements.

When the honing operation is completed, they tool is withdrawn from the work in well known manner by temporarily moving the limit switch LS-l out of the path of the switch operating member 21. When the tool head` is fully retracted, the reciprocating mechanism is stopped by closure of the valve V and the current supply to the motors M-I and M-2 is interrupted in the usual manner, as, for example, under control of the limit switch IS-Z. The iinished Work piece may then be removed from the machine.

It will be apparent from the foregoing that the invention provides a novel method of honing which enables the honing process to be employed in the dressing of tapered bores to a true contour and .smooth ilnish. The invention also provides a novel machine for carrying out the improved method in an efilcient and reliable manner. Through the medium of novel control mechanism, the pressure exerted by the tool on the surface operated on is regulated automatically in accordance with the direction in which the tool is moving relative to the work.

I claim as my invention:

1. The method of dressing elongated hollow work pieces with an expansible and contractible honing tool which comprises. relatively rotating and simultaneously relatively reciprocating the tool and a work piece, expanding the tool to exert a relatively light pressure on the work piece during relative traverse of the tool and work piece in one direction, and expanding the tool to exert a substantially higher pressure on the work piece during the relative traverse of the tool and work piece in the opposite direction.

2. The method of dressing elongated hollow work pieces with an expansible and contractible honing tool which comprises, rotating the tool, simultaneously reciprocating the tool through strokes of sufficient amplitude to traverse it from one end of the work piece to the other, expanding the tool to exert a relatively light pressure on the work piece as it is moved in one direction, and expanding the tool to exert a substantially higher pressure on the work piece as it is moved in the other direction.

3. The method of honing work pieces having elongated tapered bores which comprises, inserting an expansible and contractible honing tool in the large end of the bore, relatively rotating the tool and work, effecting relative longitudinal traverse of the tool and work piece between the ends of the bore, expanding the tool to exert a relatively light pressure on the Walls of the bore in its relative traverse toward the small end of the bore, and expanding the tool to exert a substantially higher pressure on the walls of the bore in its relative traverse toward the large end of the bore.

4. The method of honing work pieces having elongated tapered bores which comprises, inserting an expansible and contractible honing tool in the large end of the bore, relatively rotating the tool and work, repeatedly reciprocating the tool between the ends of the bore, expanding the tool to exert suflicient pressure on the Walls of the bore to enable the tool to operate thereon and yet permit the tool to contract as it moves from the large end toward the small end of the bore, and expanding the tool with a substantially higher pressure suilicient to maintain the same in continuous operative engagement with the walls of the bore as the tool moves from the small end toward the large end of the bore.

5. In a honing machine, in combination, a support for an expansible and contractible honing tool, a support for a Work piece to be operated on by the tool, means for rotating one of the supports, means for reciprocating one of the supports to effect a relative traverse of the tool from one end of the work to the other, power actuated means for expanding the tool to exert a relatively light pressure on the work piece, means for substantially increasing the pressure exerted by the tool on the work, and control mechanism operating in timed relation to the reciprocation of said one support for rendering said pressure increasing means effective when the support is moving in one direction and ineffective when the support is moving in the opposite direction.

6. In a honing machine, in combination, a support for an expansible and contractible honing tool, a support for a work piece to be operated on by the tool, means for rotating the tool, means for reciprocating the tool support to repeatedly traverse the tool from one end of the Work piece to the other, pressure fluid actuated means for expanding the tool into engagement with the work piece, a source of pressure fluid, pressure regulating means, and control means for said regulating means operated by the movements of the tool support for actuating said regulating means to vary the pressure of the fluid supplied to the tool expanding means in accordance with the direction in which the -tool support is moving.

7. In a honing machine, in combination, a support for an expansible and contractible honing tool. a support for a work piece to be operated on by the tool, means for rota-ting the tool, means for reciprocating the tool support to repeatedly traverse the tool from one end of the work. piece to the other, pressure uid actuated means for expanding the tool into engagement with the` work piece. control means for said pressure fluid actuated means operable to vary the pressure exerted by the tool on the work piece, and means actuated in response to the movements of the tool support for operating said control means.

8. In a honing machine, in combination, a support for an expansible and contractible honing tool, a support for a work piece to be operated on by the tool, means for rotating the tool, means for reciprocating the tool support -to repeatedly traverse the tool from one end of the work piece to the other, pressure fluid actua-ted means on the tool support for expanding the tool into engagement with the pork piece, a source of pressure uid, a hydraulic circuit. for delivering the pressure fluid from said source to the tool expanding means, pressure control means for varying the pressure oi' the fluid supplied to the tool expanding means including a two-position valve, and means for operating the valve to one position while the tool support is moving in one direction and for operating the valve to i-ts other position while the tool support is moving in the other direction.

9` In a honing machine, in combination, a support for an expansible and contractible honing tool, a support for a work piece to be operated on by the tool, means for rotating the tool, means for reciprocating the tool support to repeatedly traverse the tool from one end of the work piece to the other, pressure fluid actuated means for expanding the tool into engagement with the work piece, a source of pressure fluid, a hydraulic circuit for delivering the pressure uid from said source to the tool expanding means, a high pressure control valve and a low pressure control valve adapted to be associated with said hydraulic circuit selectively to regulate the pressure of the liuid supplied to the tool expanding means, and control means operated in response to the movements of the tool support for rendering one of said valves elective while the head is moving in one direction and for rendering the other valve effective when the head is moving in the opposite direction.

10. In a honing machine, in combination, a support i'or 4an expansible and contractible honing tool, a support for a work piece to be operated on by the tool, means for rotating the tool, means for reciprocating the tool support to repeatedly traverse the -tool from one end of the work piece to the other, pressure iiuid actuated means for expanding the` tool into engagement with the work piece, a source of pressure fluid, a hydraulic circuit for delivering the pressure fluid from said source to the tool expanding means, pressure control means including a valve operative in one position to lupply low pressure fluid to the tool expanding means and operative in the other position to Supply high pressure fluid thereto, said valve being biased to one of said positions, a solenoid for operating the valve to its other position, and a friction operated switch carried on the tool support and coacting with the frame of the machine in the movements of the support to energize said solenoid while the head is moving in one direction and to deenergize the solenoid while the head is moving in the other direction.

l11. In a machine for honing tapered bores, in

combination, a reciprocatory support for an exalined with the axis of the tool, means for rotating the tool, means for reciprocating the tool support to traverse the tool repeatedly through the bore from one end of the work piece to the other, power actuated means for expanding the tool into operative engagement with the walls of the bore, and control means for said power actuated means operative to cause the tool to be expanded with relatively light pressure in its movement from the large end toward the small end of the bore and to be expanded with substantially higher pressure in its return movement.

12. In a machine for honing tapered bores, in combination, a reciprocatory support for an expansible and contractible honing tool, means for supporting a taper bored work piece with its axis -alined With the axis of the tool, means for rotating the tool, means for reciprocating the tool support to traverse the tool repeatedly through the bore from one end of the Work piece to the other, pressure fluid operated means for expanding the tool into operative engagement with the walls of the bore, a source of pressure uid, and pressure control means interposed between said source and said pressure liuid operated means for holding the pressure of the fluid to -a relatively low value while the tool moves from the large end to the small end of the bore and for substantially increasing the pressure of the fluid as the tool moves back toward the large end of the bore.

13. In a machine for honing tapered bores, in combination, a reciprocatory support for an expansible and contractible honing tool, means for supporting a taper bored work piece with its axis alined with the axis of the tool, means for rotating the tool, means for reciprocating the tool support to traverse the tool repeatedly through the bore from one end of the work piece to the other, pressure fluid operated means for expanding the tool into operative engagement with the walls of the bore, a source of pressure fluid, a hydraulic circuit for delivering the iluid from said source to said fluid operated means, a high pressure relief valve. a low pressure relief valve,

a control valve operative to connect said relief valves individually to the hydraulic circuit to regulate the pressure of the fluid supplied to the fluid operated means,'and means for operating said control valve to connect the low pressure relief valve to the circuit while the tool is moving from the large end to the small end of the bore and to connect the high pressure relief valve to the circuit while the tool is moving back to the llarge end of the bore.

14. In a machine for honing tapered bores, in combination, a reciprocatory support for an expansible and contractible honing tool, means for supporting a taper bored work piece with its axis alined with the axis of the tool, means for rotating the tool, means for reciprocating the tool support to traverse the tool repeatedly through the bore from one end of the work piece to the other, pressure lluid operated means for expanding the tool into operative engagement with the walls of the bore, a source of pressure uid, a hydraulic circuit for delivering the fluid yfrom said source to said fluid operated means, a high pressure relief valve, a low pressure relief valve, a control valve operative to connect said relief valves individually to the hydraulic circuit to regulate the pressure of the fluid supplied to the iiuid operated means, a solenoid operative when energized to set said control valve to connect the high pressure relief valve to the circuit and operative when deenergized to set said control valve to connect the low pressure relief valve to the circuit, and a control switch on the tool support having a friction member cooperating with a stationary part of the machine in the movements oi' the supportl to deenergize the solenoid as the tool is advanced from the large end to the small end of the bore and to energize the solenoid dur-v ing the return movement of the tool.

15. A honing machine, in combination, an expansible and contractible honing tooll a support for said tool, a support for a vwork piece to be operated on by the tool, means for effecting relative rotation of the tool support and the work, means for reciprocating one of said supports to effect a relative traverse of the tool from one end of the work piece to the other, pressure iiuid actuated tool expanding means, a source of pressure fluid for actuating said tool expanding means, pressure regulating means associated with said source, and control means for said regulating means operative in response to the movements of the reciprocating support to actuate said regulating means and thereby vary so as to increase the pressure of the fluid supplied to the tool expanding means when the reciprocating support is moving in one direction and to. decrease the pressure oi the iluid when the reciprocating support is moving in the opposite direction.

16. A honing machine'having, in combination, an expansibleand contractible honing tool,.a support for said tool. a support for a work piece to be operated on by the tool, means for effecting relative rotation between the tool support and the work, means for reciprocating one of said supports to eiect a relative 'traverse of the tool from one end of the work piece to the other, pressure fluid actuated meansoperative to expand the tool into engagement with the work piece, a source of pressure iluid, a hydraulic circuit for delivering the pressure uid from said source to the tool expanding means, a high pressure control valve and a low pressure control valve associated with said hydraulic circuit operable selectively to regulate the pressure of the fluid supplied to the tool expanding means, and control means operative to render said pressure control valves effective alternately in timed relation to the reciprocation of said one support.

17. In a honing machine, in combination, a

' said supports, means for reciprocating one of the supports to effect a relative traverse of the tool from one end of the work piece to the other, pressure iluid actuated means operative to expand the tool into engagement with the surface ,of the work piece, means for supplying pressure uid to said tool expanding means, and control means operable automatically to alternately increase the pressure oi' the fluid supplied to the tool expanding means when the relative movement of the tool and work supports is in one direction and to decrease the pressure of the duid when the relative movement of the supports is in the opposite direction.

18. In a honing machine, in combination, a support for an expansible and contractible honing tool, a support for a Work piece to be operated on by the tool, means for rotating one of said supports, means for reciprocating one of said supports to repeatedly traverse the tool from one end of the work piece to the other, power actuated means operable to expand the tool into engagement with the work piece, a two-position control device operable in one position to effect expansion of the tool with a relatively light pressure and in the other position to eiect such expansion with a substantially higher pressure, and means for operating said control device alternately from one position to the other in response to the reciprocation of said one support.

19. A machine for honing tapered bores hav ing, in combination, a support for an expansible and contractible honing tool, a support for a taper bored work piece, means for reciprocating one of said supports to effect a relative traverse of the tool axially through the bore from one end oi' the work piece to the other, a tool expanding member, power actuated means operable to shift said member in a direction eiective to force the tool into engagement with the walls of the bore, and control means operable selectively to cause said power actuated means to exert a relatively light pressure on the tool expanding member while the reciprocatory support is moving in aA direction eiective to produce a relative movement of the tool from the large end toward the small end of the bore and to exert a substantially greater pressure on 'the member during the return movement of the reciprocatory support.

ALBERT M. JOHNSON. 

